In the current state of the art, spearguns may be divided into two classes: pneumatic spearguns and band-powered or Arbalete spearguns.
Arbalete spearguns have a continuous or discontinuous shaft guide at the top of the speargun body, thereby providing the advantage of proper aiming.
Additional advantages of Arbalete spearguns include, for example:
the possibility of using long spears, because the band is manually drawn into the firing position, and is not pushed by the spear;
the possibility of using thin spears, which are faster and cause less damage to the fish being hit;
a low weight;
a relatively simple construction;
a highly sensitive trigger;
low noise when fired, firing being only caused by release of the band;
low power loss as depth increases, as power is only provided by the compression of the band, which is typically hollow, and consequent loss of elasticity;
high load capacity, since the band is manually loaded using both arms, and back muscles can provide loads of about 50 kg.
Nevertheless, Arbalete spearguns have certain drawbacks, such as:
low power, unless multiple bands are used;
a greater overall length as compared with similar pneumatic spearguns;
vibrations of the band(s) during lateral movement of the speargun;
a loss of propelling force of the loaded band, with time and increasing depth;
no possibility of power adjustment.
In pneumatic spearguns as described hereinbefore, the slide guide typically consists of the barrel, with the spear being manually introduced therein, and the piston being pushed by the spear to the end loading position, where it is retained by a retaining system. This causes the worst drawback of pneumatic spearguns, i.e. difficult aiming, since the spear is not exposed outside the speargun in the loaded position, but is within the speargun body.
The end spear tip portion is generally outside the barrel in the loaded state, but aiming cannot be done perfectly in line with the spear shaft and hence it is altered or difficult.
Pneumatic spearguns have a number of advantages, such as:
very high power;
power adjustment features;
little or no vibration during movement;
power maintained over time;
more compact design.
Nevertheless, pneumatic spearguns also have drawbacks, such as:
difficult use of long or thin spears;
difficult loading of long spearguns;
high noise during firing;
less sensitive trigger;
loss of power with increasing depth;
limited load capacity, although a loading force of about 30 kg in a pneumatic speargun provides about 50% higher power as compared with a 50 kg loaded Arbalete speargun;
higher weight;
more complex construction;
higher cost.
In pneumatic spearguns, the barrel is filled with water in the loaded state, whereby the piston is required to push both the spear and the water between the spear and the cylinder walls, which causes a power loss.
The friction of the ejected water adds to the mass to be pushed by the piston.
For this reason, pneumatic spearguns generally have large holes in their barrel to allow water ejection.
In an attempt to obviate this drawback, “dry” pneumatic systems have been developed, in which a hydraulic seal is provided at the mouth of the barrel, typically an O-ring acting upon the side surface of the spear.
“Dry” spearguns have the advantage of avoiding the need of pushing water out of the barrel, whereby they provide higher efficiency and hence higher powers, with less noise.
Nevertheless, these spearguns have certain drawbacks such as higher complexity, lower reliability, higher costs and high wear of the seal, in addition to restrictions in the shape and functions of the spears.